In recent years, advances in technology, as well as ever evolving tastes in style, have led to substantial changes in the design of automobiles. One of the changes involves the power usage and complexity of the various electrical systems within automobiles, particularly alternative fuel vehicles, such as hybrid, electric, and fuel cell vehicles.
Many of the electrical components, including the electric traction motors used in electric and hybrid electric vehicles, receive electrical power from alternating current (AC) power supplies. However, the power sources (e.g., batteries) used in such applications provide only direct current (DC) power. Thus, devices known as power inverters are used to convert the DC power to AC power. Such power inverters are implemented using a plurality of power transistors that exhibit temperature cycling during normal use. Accordingly, a power inverter module of a vehicle may include some type of thermal protection circuit to monitor the temperature of the module.
Some conventional power modules use a temperature sensor such as a thermistor to obtain a rough estimate of the temperature of one or more transistors in the inverter module. The temperature sensor does not directly or precisely measure the actual real-time silicon temperature of the transistor(s) because the temperature sensor is not co-located with the transistor(s).